This invention relates to apparatus for measuring the moisture content of material and particularly to such apparatus which has a spaced or non-contacting relationship with the material under test.
Most capacitor means for sensing the moisture content of material tend to be sensitive to the thickness of the material or the placement of the material relative to the capacitor plates. In apparatus according to my U.S. Pat. No. 3,523,243 granted Aug. 4, 1970, sensitivity to the thickness and placement of material is reduced by coupling radio frequency energy along the length of the material between offset or non-juxtaposed plates, while ground plates are interposed to "shunt out" some of the radio frequency signal when the material more closely approaches transmitting and receiving plates. While this equipment has the advantage of improved independence of material placement relative to capacitor plate means, the range of independence is found to be relatively close proximity to the capacitor plate apparatus which can result in damage to the apparatus if struck by material measured. It is also desired to provide apparatus having a greater range of independence due to movement of the material. Therefore, lumber or similar material can be accommodated having a greater degree of warp or irregularity without equipment damage and with enhanced accuracy of output indication.